The invention generally relates to an air manager system for a metal air battery.
Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized; the cathode contains or consumes an active material that can be reduced. The anode active material is capable of reducing the cathode active material. In order to prevent direct reaction of the anode material and the cathode material, the anode and the cathode are electrically isolated from each other by a sheet-like layer, typically called the separator.
When a battery is used as an electrical energy source in a device, such as a cellular telephone, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
In a metal air electrochemical cell, oxygen is reduced at the cathode, and a metal is oxidized at the anode. Oxygen is supplied to the cathode from the atmospheric air external to the cell through one or several air access port(s) in the container.
During periods of inactivity, there is no need for air from the environment to diffuse into the cell. In fact, it is preferred that the supply of air to the cell be minimized, because the diffusion of air into the cell can lead to changes in the humidity level of the cell. When the humidity level of the outside atmosphere is lower than that of the cell, the cell can dry out. When the humidity level of the outside atmosphere is higher than that of the cell, the cell can flood. In addition, when air diffuses into the cell, the anode can become prematurely oxidized.
An air manager system enhances the activated storage life of a metal-air battery system by controlling the flow of air, which includes oxygen, carbon dioxide, and water, into and out of the system. During periods of battery use, an air mover, such as a fan, moves enough air into and out of the system to ensure good performance.
The distribution of air flow across the active surfaces of the cells can be uneven. Uneven air flow can result in xe2x80x9chot spotsxe2x80x9d in the battery, where the anode and the cathode react more than in other areas of the battery. Hot spots can lead to inconsistent battery performance and failure to realize the maximum capacity of the battery.
The air manager system of the invention provides for improved activated storage life of the battery contained in the system and provides for good performance of the battery during use. Air is directed across active surfaces of the battery evenly, thus optimizing performance. In addition, the system is designed for ease of use by the consumer.
In one aspect, the invention features an air manager system for a metal air cell. The system includes: (a) a housing having an air mover and an air outlet opening; and (b) a cartridge that is removable from the housing. The cartridge includes (i) a metal air cell; (ii) an air inlet opening located toward a first end of the cartridge and adjacent to a first side of the cartridge; (iii) an air outlet opening located toward a second end of the cartridge and adjacent to a second side of the cartridge; (iv) a first diffusion tube communicating with the air inlet opening of the cartridge, the first diffusion tube extending along the first side of the cartridge; (v) a second diffusion tube communicating with the air outlet opening of the cartridge, the second diffusion tube extending along the second side of the cartridge; (vi) a first distributor tube communicating with the first diffusion tube, the first distributor tube extending from the first diffusion tube along the first side of the cartridge through a change of direction and being adjacent to an air plenum, the first distributor tube including a plurality of openings communicating with the air plenum; and (vii) a second distributor tube communicating with the second diffusion tube, the second distributor tube extending from the second diffusion tube along the second side of the cartridge through a change of direction and being adjacent to the air plenum, the second distributor tube including a plurality of openings communicating with the air plenum.
The air mover can move air into the air inlet opening of the cartridge and/or extract air from the air outlet opening of the cartridge. The diffusion tube or tubes help to minimize the transport of water vapor into and out of the cartridge during periods of inactivity. The diffusion tubes therefore help to prevent the cells from flooding or drying out.
When the metal air cell has been depleted, the cartridge can be removed from the housing and replaced with a fresh cartridge. The housing, including the air mover, can be re-used with the new cartridge, instead of being replaced. This design helps to minimize the cost of using the air manager system. It also reduces the size of the cartridge, which in turn minimizes the amount of waste generated when the cartridge must be replaced.
In another aspect, the invention features an air manager system for a metal air cell. The system includes: (a) a housing having an air mover and an air outlet opening; and (b) a cartridge that is removable from the housing. The cartridge includes (i) a metal air cell; (ii) an air inlet opening; (iii) an air outlet opening; (iv) a first diffusion tube in communication with the air inlet opening and a second diffusion tube in communication with the air outlet opening; (v) a first distributor tube in communication with the first diffusion tube and a second distributor tube in communication with the second diffusion tube; and (vi) a first panel defining a plurality of openings communicating with the first distributor tube and a second panel defining a plurality of openings communicating with the second distributor tube. The diffusion tubes, the distributor tubes, and the openings cooperate to define a plurality of air flow paths that start at the air inlet opening of the cartridge, continue through the cartridge, and end at the air outlet opening of the cartridge. All of these air flow paths are substantially equal in length.
In another aspect, the invention features a method for controlling air flow in a metal air battery. The method includes: (a) confining at least one metal air cell within a cartridge having an air inlet opening and an air outlet opening; and (b) moving air through any of a plurality of air flow paths within the cartridge. Each of these air flow paths passes through the air inlet opening of the cartridge, through a diffusion tube, through a distributor tube, across an active surface of a cell, and through the air outlet opening of the cartridge. All of the air flow paths are substantially equal in length. The method can include moving air into the air inlet opening of the cartridge and/or extracting air from the air outlet opening of the cartridge.
Air from the atmosphere is forced into the cartridge by air discharged from an air mover, such as a blower, or pulled out of the cartridge as intake air supplied to an air mover, such as a vacuum device. It flows across the active surface of the cell contained in the cartridge, then exits the cartridge, rather than being recycled through the cartridge.
As used herein, xe2x80x9cremovablexe2x80x9d means that a component can be easily removed, for example, by a consumer, without the need for tools or excessive force.
As used herein, xe2x80x9ctowardxe2x80x9d means at a position on a member, relative to a given point on that member, within 30%, more preferably 20% or 10%, of the total length of the member. A feature located toward an end of a bar having a length of 10 cm is within 3 cm of that end of the bar, and is preferably 2 cm or 1 cm from the end.
Other features and advantages of the invention will be apparent from the description of the preferred embodiment thereof, and from the claims.